I've spent the last month or so looking at all the discussions re direct laser printing on boards. There are all sorts of warnings, nay sayers, etc who say it can't work. Then I saw the post and site of laserpcb, where Dave says (he has a patent)that he can print on copper foil using his special "gel" then glue it to FR4 to make a PCB. So, if it is possible to put toner on copper foil, it should be possible to put it on boards directly.
I took a Samsung ML-2510 and modified the paper path to be straight and flat, and moved the feed sensor (also inverted it) then I simply ran a board through. No problem. A few sparks, but the image seems very good, no distortion, very crisp. I tried Dave's Gel (sorry Dave), but the image seems identical with and without the gel.
I haven't finished experimenting, which is why I wanted the test pattern. I seem to easily be able to print 1 mil traces, but I'm not sure yet of the spacing I can use, though I would guess 5-8 mil.
The board comes out of the printer with the toner as powder electrostatically stuck to the board, so it has to be fused. I am reluctant to use the fuser on the printer for several reasons. One is that it is a pain to move it to a flat path - I would have to move a gear, among other things. Secondly, the speed might easily be too fast to fuse the toner. Also, if the toner is smudged or not perfect, it is very easy to wipe and reprint the board if it isn't fused.
An advantage of fusing it is that it (hopefully) will be stuck in place, even if it isn't fused completely. Obviously there is a lot of work to do here.
I think I have demonstrated that direct laser printing of pcb's is possible. If anyone wants further information, I will be happy to share.
Mark
-----Original Message-----
>From: listgroups08@...
>Sent: Mar 26, 2008 7:30 PM
>To: Homebrew_PCBs@yahoogroups.com
>Subject: Re: [Homebrew_PCBs] Laminator Questions
>
>Hello Mark,
> I am an ex printer technician and I have been toying with
>the concept of direct printing with a laser for the last couple of days.
>
>What concerned me is that the conductivity of the copper on the PCB was
>likely to cause the image on the PCB to be blurred or poorly focused along
>the Y axis.
>
>In normal operation with paper the image is transferred from the drum to the
>page by a single line (wire) across the X axis. Manufacturers go to some
>trouble to make this wire as thin as possible and ground two parallel lines.
>This improves Y focus and I expected this would become a problem due the
>conductive copper coating.
>
>I am very interested to hear what your experiments are revealing.
>
>If you are using the image drum and you have the above problem then you need
>to provide shielding above and below the point on the image drum that is
>closest to the PCB.
>
>Ideally the shielding voltage should be further away from the from PCB
>voltage than the image drum itself. The easiest way to achieve this is
>probably have a divider on the HT side and upping the actual HT.
>
>I am a bit rusty on the theory so please let me know if this is the problem
>and I will do my revision and get back to you with a mode detailed
>information.
>
>If this is simply a fusing problem, ie the image is fine on the PCB then
>there could be a number of causes.
>
>Firstly there are two types of fuser today and the laminator may be the more
>modern type.
>
>The older type used a heated roller and often this roller had a soft
>coating, this type is ideal for what you want as it will provide an even
>pressure to the toner. It will also work better at a lower temperature
>(desirable) as it will have a greater surface area of physical contact.
>
>The older type that had a solid roller is less suitable as the two hard
>surfaces together will cause uneven pressure and the reduced surface contact
>will require more temperature which in turn increases the probability of
>blurring.
>
>Fuser temperature needs to be accurate. All fusers have a temperature sensor
>and are closely regulated.
>
>The older type where good but had two problems for normal printer use.
>1) Heating a whole roller took a lot more energy.
>2) The complete roller has far more thermal mass and it takes time to get
>the higher thermal mass to an accurate temperature. This caused long delays
>before the printer could print its first page after power on or standby and
>this delay is an important spec to manufacturers.
>
>The newer type works completely differently. The roller is somewhat
>flattened on the side that contacts the paper and does not revolve. Around
>this roller is a film of thermally conductive material that can revolve
>around the roller to allow the paper free movement. There is thin strip
>heating element below the thermally conductive film that can change in
>temperature very rapidly doe to it's low thermal mass.
>
>I doubt this newer type is any good for what you want for two reasons -
>1) It is not very pliable and would probably cause uneven pressures.
>2) It is not very robust and I would expect the edges of the PCB to wear
>into it very quickly.
>
>The older type with the hard roller is probably not much good either due to
>uneven pressure and higher required temperatures.
>
>The older type with the soft roller would be ideal.
>
>I don't know what is in the laminator you have. Or even if that have any
>form of temperature regulation. Very crude regulation could be done with a
>light dimmer but two warnings on this. Don't even try it if you are not
>experienced with electrical things or you have no safety breakers on you
>power supply (RCD, CBR) etc. And The power requirements for the laminator is
>likely to be several hundred watts and most light dimmers do not go up that
>far.
>
>Some other thoughts I have been thinking are to do away with the image
>transfer all together. Perhaps the image unit could still be used to provide
>an even coating of toner to the complete surface of the PCB. The new scanner
>would be installed with a high powered laser and an optical attenuator
>placed in the path for the syntonisation sensor to prevent damage to it by
>the higher power.
>
>It idea is that the scanners laser provide the power to fuse the toner to
>the board and rest of the toner is just removed by blowing it a way.
>
>I haven't the math for it yet so I don't know what power laser would be
>required.
>
>The power to the toner at any point is the product of the laser power and
>the time. The faster the scanning the lower the effective power. However on
>the other hand is the scanners need for speed. The scanner accuracy is
>dependent on its inertia which is the product of rotational mass by the
>rotational speed squared. So obviously there are limits that will dictate
>the minium laser power required.
>
>Thanks.
>
>----- Original Message -----
>From: "Mark Lerman"
>
>Well, I'm not doing toner transfer, actually, I'm using a modified
>laser printer to print directly on the board - the toner is still in
>powder form, so it is relatively easy for it to smudge. I suspect
>I'll have to use a hot plate and directly compress the board between
>two plates using a teflon sheet between the toner and the top plate.
>The laminator caused only a little smudging, but it was my first
>attempt and I used the carrier. Perhaps just a teflon sheet will
>allow use of the laminator. We'll see.
>
>Mark
>
>
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